Esters over cu-zn-ai catalysts



millimeters in diameter.

Unite HYDROGENOLYSIS F ALllPI-TATIC ACIDS AND ESTERS (EVER Cu-Zn-=Al CATALYSTS No Drawing. Application July 2, 1956 Serial No. 595,079

Claims priority, application Germany .luly 8, 1955 11 Claims. (Cl. 260-635) This invention in general relates to hydrogenolysis of aliphatic monoor dicarboxylic acids or esters thereof to form aliphatic monohydric or dihydric alcohols and, more particularly, to continuous as well as batch hydrogenolysis of said aliphatic acids or esters and improvements in catalysts used therein.

Hydrogenolysis of aliphatic acids or esters is a reaction in Which the acids are reduced to form aliphatic alcohols. Among the most important commercial applications of this process is the conversion of coconut oil fatty acid glyceryl esters to alcohols, the most important being lauryl alcohol, which alcohols are then reacted with sulfuric acid and neutralized to produce a detergent composition, e. g., sodium lauryl sulfate. The alcohols can also be used as intermediate products, for example,

in the production of the corresponding chloro hydrocarbons or dichloro hydrocarbons, and they are important intermediate products for the production of steeping and textile auxiliary agents. The higher fatty alcohols also find use in pharmaceutical and cosmetic preparation as, for example, the base of a salve.

It is known that aliphatic monoand dicarboxylic acids can be reduced to the alcohols at a hydrogen pressure exceeding 100 atmospheres gauge with the employment of copper chromite or zinc chromite catalyst. In the customary continuous hydrogenolysis process, it is necessary to employ catalytic bodies such as irregularlyshaped pieces, pills, rings, etc., whereby the substance to be treated is brought into intimate contact with the catalyst in a bed in a tube-shaped oven. It is not always possible to obtain the foregoing catalysts in defined forms because they are fine powders which cannot be formed effectively as active catalysts in the .desired size either through pressing under high pressure or through :addition of binders.

In the present invention we have discovered a catalyst made of an alloy of zinc, copper and aluminum which can be easily produced by fusion of the components in an inert atmosphere. The hardened alloy can be broken up into irregular pieces of the desired size, can be molded in any desired form, or can be reduced to any grain size desired, from a fine powder to pieces of several The alloy is thereafter placed 'in contact with an alkali medium whereby the alloy is activated by corrosion thereof. We have discovered that the reduction of aliphatic monocarboxylic acids having as low as 2 and as high as 18 or more carbon atoms or dicarboxylic acids having 2 to 12 carbons or their esters proceeds very successfully in three or more hours at a hydrogen pressure between 100 and 500 atmospheres gauge and at a temperature between 180 C. and 350 C. when the reaction is catalyzed by the catalysts described herein. Dihydric alcohols result from hydrogenolysis of corresponding 'dicarboxylic acids having at least 4 carbons.

More particularly, the catalysts of the present inventio comprise alloys of zinc, copper and aluminum superficially corroded with lye. The zinc content may range ICC between 5 and 40% by weight, copper between 30 and 60% by weight and aluminum between 30 and 60% by weight. Our preferred catalyst comprises 20% zinc, 40% copper and 40% aluminum. The alloys are activated at temperatures between 50 and C. by contact with a caustic soda or caustic potash solution for 10 to minutes, depending upon the size of the individual pieces. if contact is maintained for more than onehour, the expended lye is drained off and replaced with fresh caustic after about an hour. Thereafter the activated catalyst is freed from water by washing with methapol or other suitable solvent for removal of water from the surface of the alloy. During the washing, air must be excluded because the catalyst is deactivated by contact with air.

At temperatures between C. and 350 C. the hydrogenolysis employing the aforesaid catalysts may proceed either in a discontinuous or batch process in stirring or rotating type autoclaves or in a continuous process. In the latter case the alloys are used in the form of irregular or preformed pieces in a catalytic bed. In the continuous process the acid or ester is dissolved in methanol or other alcohol and, in admixture with excess hydrogen at a pressure of 200-400 atmospheres, is passed through a reactor tube in contact with the catalytic bed at temperatures ideally between 200300 C. Intimate contact between the acid, hydrogen, and catalyst is best achieved by passing the acid through the reactor tube filled with small pieces of the catalyst while hydrogen is circulated through the tube by means of a recirculating pump. The reaction mixture then is passed through a cooler into a separator in which the gaseous phase is separated from the liquid phase. Thehydrogen is conducted back over through a circulating pump and preheater into the reaction tube, and the expended hydrogen is replaced by means of a compressor for maintenance of constant pressure. The reduced products comprising essentially the alcohol are drawn off from the separator at a rate so as to maintain the liquid level in the separator constant. The product so removed is freed of dissolved hydrogen in a degassing vessel, and the components are immediately distilled to yield the alcohol.

If the catalyst becomes deactivated after considerable use in the continuous process, it is reactivated with preheated caustic at 50-100 C. after the pressure is relieved and the contents removed from the reaction tube. The caustic is run off after 15-60 minutes contact period, the length of contact depending upon the concentration of the alkali. If necessary, the superficial corroding is repeated with fresh alkali. Thereafter the catalyst bed is rinsed with distilled water for a suflicient time to insure that all alkali is removed and thereafter with'methanol. The superficial corroding can be repeated 10 or 20 times during the life of the catalyst.

Powdered catalysts may be employed in a batch process and must be separated. from the resulting reaction mixture after hydrogenolysis by filtering or centrifuging at a temperature at which the reaction mixture is liquid. They are, likewise, activated and reactivated by a caustic for which a heated stirring kettle is used. With powdered catalysts the acting time of the caustic is, because of the greater surface, correspondingly shorter.

The invention will be illustrated but is not limited by the following examples.

Example I Into 400 grams of a 20% aqueous solution of caustic soda at 50 C. there is added over a period of 15 minutes with stirring, 60 grams of a finely pulverized alloy composed of 40% aluminum, 40% copper and 20% zinc. Contact between the caustic soda and alloy is maintained for an additional minutes at C. The thus activated catalyst is washed by repeated decanting with water to remove the lye and thereafter the water is displaced with methanol. In a shaking autoclave of 2 liters capacity, 500 grams of adipic acid dimethyl esters are added, and thereafter the methanol-moist catalyst is added. The autoclave is closed while being rinsed with nitrogen, and the air is completely removed. Hydrogen is introduced into the autoclave until a pressure of 200 atmospheres is obtained. As the autoclave is agitated, hydrogcnolysis is achieved during a six-hour reaction period 260 C. After cooling and release of pressure of the autoclave, the catalyst is removed by filtration or by centrifuging. The reaction mixture, after the methanol and a small amount of n-hexanol1 have been removed by distillation, is distilled in a vacuum at 144 C. and 15 millimeters pressure. As a result 292 grams (86% of theory) of hexane diol-1,6 distil over. The melting point of hex ane diol 1,6 is between 41 and 42 C.

Example II Hydrogenolysis of 500 grams of adipic acid dimethyl esters was accomplished in the same manner as in Example I with'the addition of grams of a catalyst of 55% aluminum, 40% copper and 5% Zinc superficially corroded as in Example I. The yield was 261 grams (77% of theory) of hexane diol 1,6. As a by-product, thirty-one grams of n-hexanol-1 were obtained.

Example III Five hundred grams of adipic acid were reacted as in Example I. The catalyst was an alloy of 40% copper, 30% aluminum and 30% zinc superficially corroded as in Example I. The yield was 237 grams of hexane diol 1,6 of theory).

Example IV One hundred grams of sebacic acid dissolved in 100 grams methanol were put in a 1 liter rotating autoclave. Thirty grams of a superficially corroded pulverized alloy of 40% aluminum. 40% copper and 20% zinc as in Example I were added. Hydrogenolysis at a pressure of 200 atmospheres was ceased after six hours at 320 C. Distillation of the reaction product yielded 41 grams of decandiol at a boiling point of 176 C./l5 mm., the diol having a melting point of 71 C. As a by-product, 11 grams of n-decanol-l were obtained.

Example V In a rotating autoclave were placed 1,000 grams of pimelic acid and grams of a catalyst of 40% aluminum, 40% copper and 20% zinc superficially corroded with lye. Hydrogenolysis of the acid proceeded at a pressure of 200 atmospheres for 5 hours at 280 C. After separation of the catalyst by centrifuging a methanol solution of the reaction product and distilling off the methanol. there was isolated as a reaction product, through fractional distillation in a vacuum, 583 grams (83% of theory) of heptane diol 1,7 with a boiling point of 164 C./15 mm. and a melting point of 64 C.

Example VI Following the procedure in Example I, 1,000 grams of succinic acid methyl esters were reacted for 4 hours at 260 C. and 200 atmospheres pressure in the presence of 80 grams of an alloy, activated as in Example I, of 40% copper, 40% aluminum and 20% zinc. From the reaction product 211 grams of butane diol-1.4 with a melting point of 19 C. and 11 214467 were isolated by distillation at 128 C./15 mm.

Example VII Four and one-half liters of an alloy of 40% copper, 40% aluminum and 20% zinc reduced to pieces of 6 to 8 mm. were put in the contact tube of a continuous hydrogenation apparatus. The contact tube was heated to 50 C., and the alloy was activated by one hours action of a 10% sodium hydroxide solution preheated to 50 C. The lye was then run oil, and the catalyst was rinsed with warm water until the water running off was neutral. Thereupon the water was removed by rinsing with methanol, the contact tube closed and the apparatus, after rinsing the tube with nitrogen, was filled with 300 atmospheres gauge of hydrogen. With the aid of a highpressure liquid pump 1 liter per hour of 50% solution of adipic acid dimcthyl esters, which was heated by a liquid-heated prc-heatcr to 270 C., was pumped into the contact tube, which was electrically heated to 270 C. The gas circulating pump was immediately started; 16 cubic meters of hydrogen at the given pressure of 300 atmospheres gauge were pumped hourly through the contact tube in a continuous stream. The hydrated product emerged from the bottom of the vertical contact tube with the excess hydrogen, ran through a cooler and thence a separator, in which the gaseous phase was separated from the liquid phase. The liquid produced was continuously depressurized and collected over a degassing vessel, while the hydrogen was conducted back to the circulating pump. With the aid of a compressor the expended hydrogen was replaced so that the pressure of 300 atmospheres was maintained. The collected product was purified by distillation. The conversion amounted to 94%. The 6% unreacted esters were conducted back to the hydrogenation apparatus. The production of hexane diol with a melting point of 41 to 42 C. and a boiling point of 114/15 mm. was at about 95% of theory of the converted product, while as a by-product 5% n-hexanol-l was isolated.

Example VIII The reaction tube of a continuous hydrogenation apparatus was filled, as in Example VII, with a catalyst of 40% aluminum, 40% copper and 20% zinc and was activated and rinsed in the same manner. The apparatus was filled with hydrogen, and 70 kg. of methyl stearatc were pumped over the preheater heated to 300 C. into the tube at an hourly rate of 0.75 to 1 liter. The temperature in the tube was set at 300 C. The gas circulation amounted to 16 cubic meters per hour. The pressure was kept at 300 atmospheres gauge. The continuously separated reaction product was purified by fractional vacuum distillation after separation from methanol. The conversion was about 89%. The unconverted esters were conducted back to the reactor. The reaction product consisted of 54 kg. stearyl alcohol (97% of theory) with a boiling point of to /1 mm., as well as 1.2 kg. of octadecane.

Example IX Five hundred g. of beef tallow were put in a shaking autoclave together with a catalyst, activated as in Example I, of 40% aluminum, 40% copper and 20% zinc, put under pressure with hydrogen at 200 atmospheres and reacted at a temperature of 200 C. for 8 hours. The hydrogenated product was boiled with methanol, filtered off from the catalyst, the methanol displaced, and the remainder distilled in a vacuum. In the vacuum distillation 430 g. of a fatty alcohol mixture were obtained, with a boiling point of 136 to 150/1 mm.

The invention is hereby claimed as follows:

1. In a method for producing aliphatic monohydric and dihydric alcohols by hydrogenolysis, at a pressure between 100 and 500 atmospheres gauge and a temperature between 180 C. and 350 C., of a member from the group consisting of monocarboxylic, aliphatic acids having at least two carbons, dicarboxylic, aliphatic acids having 2-12 carbons, and esters of the aforesaid acids, the improvement which comprises: effecting hydrogenolysis in the presence of small, alkali-corroded particles of an alloy consisting essentially of by weight 540% Zinc, 3060% copper and 30-60% aluminum.

2. In a method for reducing aliphatic monocarboxylic aseaeas acids, dicarboxylic acids and esters thereof, the improvement which comprises: intimately contacting hydrogen gas, at a pressure between l and 500 atmospheres gauge, and a composition from the group consisting of monocarboxylic, aliphatic acids having at least two carbons, dicarboxylic, aliphatic acids having 2-12 carbons and esters of the aforesaid acids at a temperature between 180 C. and 350 C. in the presence of small, alkali-corroded particles of an alloy consisting essentially of by weight 5-40% zinc, 30-60% copper and 30-60% aluminum to produce aliphatic alcohols.

3. in a method for producing aliphatic monohydric and dihydric alcohols by hydrogenolysis, at a pressure between 100 and 500 atmospheres gauge and a temperature between 180 C. and 350 C., of a member from the group consisting of monocarboxylic, aliphatic acids having at least two carbons, dicarboxylic, aliphatic acids having 2-l2 carbons, and esters of the aforesaid acids, the improvement which comprises: effecting hydrogenolysis in the presence of small, alkali-corroded particles of an alloy consisting essentially of by weight approximately zinc, 40% copper and 40% aluminum.

4. in a method for reducing aliphatic monocarboxylic acids, dicarboxylic acids and esters thereof, the improvement which comprises: intimately contacting hydrogen gas, at a pressure between 100 and 500 atmospheres gauge, and a composition from the group consisting of monocarboxylic, aliphatic acids having at least two carbons, dicarboxylic, aliphatic acids having 2-12 carbons and esters of the aforesaid acids at a temperature between 180 C. and 350 C. in the presence of small, alkali-corroded particles of an alloy consisting essentially of by weight approximately 20% zinc, 40% copper and 40% aluminum to produce aliphatic alcohols.

5. A continuous process for reducing a member from the group consisting of aliphatic, monocarboxylic acids having at least two carbons, aliphatic, dicarboxylic acids having 2-12 carbons, and esters thereof which comprises: flowing one of the aforesaid compositions slowly through a catalytic bed comprising small, alkali-corroded particles of an alloy consisting essentially of by weight 5-40% zinc, Sift-60% copper and -60% aluminum while simultaneously circulating hydrogen gas at a pressure between 100 and 500 atmospheres gauge through said catalytic bed at a reaction temperature between 180 C. and 350 C. whereby said acids and esters are reduced to aliphatic alcohols, and thereafter separating the gas and the reaction products.

6. A continuous process for reducing a member from the group consisting of aliphatic, monocarboxylic acids having at least two carbons, aliphatic, dicarboxylic acids having 2-12 carbons, and esters thereof which comprises: flowing one of said compositions slowly through a catalytic bed comprising small, alkali-corroded particles of an alloy consisting essentially of by weight approximately 20% zinc, copper and 40% aluminum while simul taneously circulating hydrogen gas at a pressure between 100 and 500 atmospheres gauge through said catalytic bed at a reaction temperature between 180 C. and 350 C. whereby said acids and esters are reduced to aliphatic alcohols, and thereafter separating the gas and the reaction products.

7. In a method for producing aliphatic, monohydric and aliphatic, dihydric alcohols, the steps which comprise: mixing aqueous caustic solution and small parlcles an alloy consisting essentially of by weight 5-40% zinc, 30-60% copper and 30-60% aluminum for a period sufiicient to corrode said alloy particles; removing the aqueous caustic; dehydrating the surfaces of the particles under conditions whereby air is excluded from contact with said alloy particles; and thereafter commingling at a pressure between 100 and 500 atmospheres gauge and a temperature between 180 C. and 350 C. hydrogen gas and a composition from the group consisting of monocarboxylic, aliphatic acids having at least 2 carbons, dicarboxylic, aliphatic acids having 2-12 carbons, and esters of the aforesaid acids in the presence of said small particles of an alkali-corroded alloy whereby said aliphatic acids and esters are reduced to aliphatic alcohols.

8. In a method for producing aliphatic, monohydric and aliphatic, dihydric alcohols, the steps which. comprise: mixing aqueous caustic solution and small particles of an alloy consisting essentially of by weight 5-40% zinc, 30-60% copper and 30-60% aluminum for a period sufficient to corrode said alloy particles; removing the aqueous caustic; dehydrating the surfaces of the particles under conditions whereby air is excluded from contact with said alloy particles; and thereafter intimately contacting hydrogen gas at a pressure between and 500 atmospheres gauge and a composition from the group consisting of monocarboxylic, aliphatic acids having at least 2 carbons, dicarboxylic, aliphatic acids having 2-12 carbons and esters of the aforesaid acids at a temperature between C. and 350 C. in the presence of said small particles of alkali-corroded alloy whereby said aliphatic acids and esters are reduced to aliphatic alcohols.

9. In a method for producing aliphatic, monohydric and aliphatic dihydric alcohols, the steps which comprise: mixing aqueous caustic solution and small particles of an alloy consisting essentially of by weight 540% zinc, 30-60% copper and 30-60% aluminum for a period of 10-120 minutes to corrode said alloy particles; removing the aqueous caustic; dehydrating the surfaces of the particles under conditions whereby air is excluded from contact with said alloy particles; and thereafter commingling at a pressure between 100 and 500 atmospheres gauge and a temperature between 180 C. and 350 C. hydrogen gas and a composition from the group consisting of monocarboxylic, aliphatic acids having at least 2 carbons, dicarboxylic, aliphatic acids having 2-12 carbons, and esters of the aforesaid acids in the presence of said small particles of alkali-corroded alloy whereby said aliphatic acids and esters are reduced to aliphatic alcohols.

10. In a method for producing aliphatic, monohydric and aliphatic dihydric alcohols, the steps which comprise: mixing aqueous caustic solution and small particles of an alloy consisting essentially of by weight 5-40% zinc, 30-60% copper and 30-60% aluminum for a period of 10-120 minutes to corrode said alloy particles; removing the aqueous caustic; dehydrating the surfaces of the particles under conditions whereby air is excluded from contact with said alloy particles; and thereafter intimately contacting hydrogen gas at a pressure between 100 and 500 atmospheres gauge and a composition from the group consisting of monocarboxylic aliphatic acids having at least 2 carbons, dicarboxylic, aliphatic acids having 2-12 carbons and esters of the aforesaid acids at a temperature between 180 C. and 350 C. in the presence of said alkali-corroded alloy whereby said aliphatic acids and esters are reduced to aliphatic alcohols.

11. In a continuous process for producing aliphatic, monohydric and aliphatic, dihydric alcohols wherein a catalytic bed is employed, the steps which comprise: contacting a catalytic bed of small particles of an alloy consisting essentially of by Weight 5-40% zinc, 30-60% copper and 30-60% aluminum with an aqueous solution of alkali for a period sufficient to corrode the particle surfaces of said alloy; removing the excess alkali; dehydrating the particle surfaces under conditions whereby air is excluded from contact with said alloy; and thereafter flowing slowly through said alkali-corroded catalytic bed a composition from the group consisting of monocarboxylic, aliphatic acids having at least two carbons, dicarboxylic acids having 2-12 carbons, and esters thereof while simultaneously circulating hydrogen gas at a pressure between 100 and 500 atmospheres gauge through said catalytic bed at a reaction temperature be- 7 tween 180 C. and 350 C. whereby said acids and esters are reduced to aliphatic alcohols, and thereafter separating the gas and the reaction products.

References Cited in the file of this patent UNITED STATES PATENTS 2,504,497 Charles et a1 Apr. 18, 1950 2,604,455 Reynolds et al. July 22, 1952 FOREIGN PATENTS 875,519 Germany Mar. 19, 1953 1,097,927 France Feb. 23, 1955 749,069 Great Britain May 16, 1956 8 OTHER REFERENCES Degering: Outline of Organic Chemistry" (6th ed, 1951), Barnes & Noble, New York, N. Y.; pp. 385-6.

5 Groggins: Unit Processes in Organic Chemistry (4th ed), McGraW-Hill, New York, N. Y., 1952, pp. 496, 509-20, 531-3, 538-9.

Ohta et al.: Repts. Govt. Chem. Ind. Research Inst.,

10 Tokyo, vol. 48, pp. 121-32 (1953).

Sam et al: Chemical Soc. of Japan, Bulletin, vol. 28, pp. 182-5 (1955). 

1. IN A METHOD FOR PRODUCING ALIPHATIC MONOHYDRIC AND DIHYDRIC ALCOHOLS BY HYDROGENOLYSIS, AT A PRESSURE BETWEEN 100 AND 500 ATMOSPHERES GAUGE AND A TEMPERATURE BETWEEN 180*C. AND 350*C., OF A MEMBER FROM THE GROUP CONSISTING OF MONOCARBOXYLIC, ALIPHATIC ACIDS HAVING AT LEAST TWO CARBONS, DICARBOXYLIC, ALIPHATIC ACIDS HAVING 2-12 CARBONS, AND ESTERS OF THE AFORESAID ACIDS, THE IMPROVEMENT WHICH COMPRISES: EFFECTING HYDROGENOLYSIS IN THE PRESENCE OF SMALL, ALKALI-CORRODED PARTICLES OF AN ALLOY CONSISTING ESSENTIALLY OF BY WEIGHT 5-40% ZINC, 30-60% COPPER AND 30-60% ALUMINUM. 